docs: tighten install section + fix stale roster rows (#17)

Install section was 22 lines with two paths, an auto-create explanation,
and a multi-line Python note. Cut to 7 lines: one command, one usage
line, one disclaimer. Per-project install still works via
`hyperresearch install` — just not documented in the lead, since 99%
of users want global.

Roster fixes:
- hyperresearch-fetcher: Haiku → Sonnet (matches actual model in hooks.py)
- hyperresearch-draft-orchestrator: Sonnet → Opus (matches actual model)

Co-authored-by: Jordan <jordanlgibbs@gmail.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>